ENH1292 Biology and Management of Dodder (Cuscuta spp.) in Ornamental Crop Production and Landscapes1 Kaley Mierek, Chris Marble, Nathan Boyd, and Shawn Steed2 Introduction Habitat Dodder are a group of over 150 species in the genus Dodder is a parasitic plant that has a wide variety of host Cuscuta. Dodder is a leafless, parasitic weed that relies plants, including agricultural crops, ornamentals, weeds, on its host for survival. These species have a wide variety and other plants. Dodder can be found in agricultural of host plants, including landscape and nursery grown crops, fields, woodlands, landscapes, and other locations ornamentals. This EDIS publication was developed to where suitable hosts are growing. help commercial growers, landscape professionals, and homeowners identify and manage dodder infestations in Distribution their greenhouses, nurseries, or landscapes. There are over 150 species of the Cuscuta genus distributed throughout the world. Most of the species are found Species Description primarily in the Americas, from Canada to South America, but certain species also occur in Europe and Asia. Ten Family species have been verified in Florida (Holm, Doll, Holm, Convolvulaceae (morning glory family) Panch, & Herberger, 1997; Lanini & Kogan, 2005; Wunder- lin, Franck, & Essig, 2017). Other Common Names Strangle weed, hairweed, hellbine, angel’s hair Growth Habit Seedlings germinate and emerge from the soil and begin to Life Span coil around a host plant. They have a vining growth habit Dodder is classified as a summer annual. Upon germination and grow in a counter-clockwise direction. Once a seedling in the spring or summer, seedlings have approximately 5 to attaches to a host plant, it will support its own weight by 10 days to attach themselves to a nearby host plant. If they forming multiple attachments with the host or adjacent do not find a suitable host within this time, the seedlings plants nearby (Figure 1). Once fully established, thick mats will die, as they depend upon the host for survival. of dodder stems can completely cover a host plant (Lanini, Cudney, Miyao, & Hembree, 2010) (Figure 2). 1. This document is ENH1292, one of a series of the Environmental Horticulture Department, UF/IFAS Extension. Original publication date May 2018. Revised March 2021. Visit the EDIS website at https://edis.ifas.ufl.edu for the currently supported version of this publication. 2. Kaley Mierek, former research assistant, UF/IFAS Mid-Florida Research and Education Center; Chris Marble, assistant professor, Environmental Horticulture Department; Nathan Boyd, associate professor, Horticultural Sciences Department; and Shawn Steed, multi-county environmental horticulture production agent II, UF/IFAS Extension Hillsborough County; UF/IFAS Extension, Gainesville, FL 32611. The Institute of Food and Agricultural Sciences (IFAS) is an Equal Opportunity Institution authorized to provide research, educational information and other services only to individuals and institutions that function with non-discrimination with respect to race, creed, color, religion, age, disability, sex, sexual orientation, marital status, national origin, political opinions or affiliations. For more information on obtaining other UF/IFAS Extension publications, contact your county’s UF/IFAS Extension office. U.S. Department of Agriculture, UF/IFAS Extension Service, University of Florida, IFAS, Florida A & M University Cooperative Extension Program, and Boards of County Commissioners Cooperating. Nick T. Place, dean for UF/IFAS Extension. Figure 3. Dodder seedlings emerging (left) and beginning to attach to a coleus plant. Credits: Kaley Mierek, UF/IFAS Shoot The stems of dodder are very thin. As the plant matures, it may become a golden yellow or remain a yellowish-green color. Dodder produces very little to no chlorophyll and relies upon its host for water and nutrients. The portion of the stem that was connected to the soil degrades as the vine migrates up the host plant, eventually being free of the soil and reattaching itself completely to the host plant (Figure 4) Figure 1. Dodder stems wrapping around pentas and forming multiple attachment points using haustoria. (Ashigh & Marquez, 2010). Credits: Kaley Mierek, UF/IFAS Figure 4. Once dodder has attached itself to a host plant, its connection to the soil withers away and it becomes completely reliant Figure 2. Dodder can spread vegetatively from one plant to another if upon the host for survival. the two host plants are close. Credits: Kaley Mierek, UF/IFAS Credits: Kaley Mierek, UF/IFAS Roots (Haustoria) Seedling Dodder has no true roots. In order to attach to a host plant, dodder plants form specialized structures called “haustoria” Seedlings are thin, twining, leafless, and vary in color from that invade the vascular tissues of host plants and allow the orange to yellow (Ashigh & Marquez, 2010) (Figure 3). dodder plant to utilize nutrients and water from the host plant (Kaiser, Vogg, Furst, & Albert, 2015). Biology and Management of Dodder (Cuscuta spp.) in Ornamental Crop Production and Landscapes 2 Inflorescence seed production can occur in the late spring throughout Flowers are small, bell-shaped, and range from yellow to fall. Although dodder is a summer annual, many species white. They emerge in clusters from summer to fall. Each have the ability to over-winter within host tissues (as flower produces one to four seeds. haustoria) and regrow the following spring (Hutchinson & Ashton, 1980; Sandler, 2010). Fruit and Seeds Impacts to the host plant can vary depending on the host Dodder produces small, pea-shaped fruit. Seeds can vary species and its stage of development when the infestation in size depending on the species, but are typically 1/16 of occurs. Seedlings and young plants will be much more an inch and are light- to medium-brown in color. Seeds susceptible than established plants. Dodder does not usu- can remain viable in the soil for more than 10 years, and, ally kill its host, but death can occur in severe cases. Plant as a result, it is important to remove plants prior to seed growth will also be reduced, and dodder causes obvious production. aesthetic issues in ornamental settings. Infestations can also stress host plants, making them more susceptible to disease Similar Species and insect damage. Leafless swallow-wort (Cynanchum scoparium) can some- times be mistaken for dodder because it is also a thread-like Management vine that experiences leaf loss with age. Leafless swallow- wort vines are typically thicker than dodder and are green. Physical and Cultural Control Love vine (Cassytha filiformis) (Figure 5) is a parasitic plant Prevention and sanitation is the best control option for this found in Florida that can easily be mistaken for dodder. species. Clean equipment thoroughly if it has been used The primary difference is that love vine tends to climb and in infested areas. In nursery and greenhouse situations, parasitize large woody plants and shrubs, whereas dodder remove and destroy the host plant once it is infested with tends to spread closer to the ground on herbaceous plants dodder. Inspect liners and new plant shipments to ensure (Nelson, 2008). that none of the plants entering the production facility are infested. Hand removal is typically not effective because dodder can regrow from small stem fragments left behind. It is also important to scout regularly to ensure that dodder has not infested weeds or other plants growing in non-crop areas. Cuscuta species (other than native species) are both Florida and federal noxious weeds, meaning that it is unlawful to introduce, multiply, possess, move, or release any living state of the plant (including seeds). Nursery crops can be quarantined if this weed is found on inventory. In the landscape, small infestations may be controlled by hand weeding, but this is rarely effective. It is usually more effective to remove the host and the dodder simultaneously. If only a small portion of a plant is infested, pruning the Figure 5. Love vine (Cassytha filiformis) is also a parasitic weed common in landscapes and is similar in appearance to dodder. host below the point of attachment can be an effective Credits: Edward L. Barnard, Florida Department of Agriculture and management option, but may result in disfiguring the Consumer Services ornamental. In areas where dodder is problematic, planting non-host plants can reduce dodder infestations. Most Plant Biology monocotyledonous species (e.g., flax lily, mondo grass, Dodder plants depend on their host for survival, but seeds liriope, and ornamental grass species) are not susceptible germinate independently of host plants. Germination to dodder infestations. Research at North Carolina State can be variable depending upon dodder species, but will University has shown that certain annual bedding plants, generally be highest during spring and summer months, including scaevola, verbena, gomphrena, and sweet potato as overwintering may be needed to break seed dormancy. (Ipomoea spp.), are not preferred hosts of dodder, while Research on C. campestris showed highest levels of germi- petunias and snapdragons are more susceptible (Neal, nation occur at temperatures of 85 to 90°F. Flowering and 2006). Biology and Management of Dodder (Cuscuta spp.) in Ornamental Crop Production and Landscapes 3 Chemical Control References Dinitroanline herbicides, including prodiamine (Bar- Ashigh, J., and E. E. Marquez. 2010. “Dodder (Cuscuta ricade), pendimethalin (Pendulum), Treflan (trifluralin),